Appearance classification of valves

Valves can be roughly divided into valves, check valves, cocks, ball valves, butterfly valves, diaphragm valves, special valves (safety valves, relief valves, vacuum valves and steam traps).

Gate valve

The valve plate moves in a direction perpendicular to the flow direction of the fluid, and the valve plate is used to open and close the flow.

The advantage is that the size between the two faces of the gate valve (the distance between the sealing surface of the valve and the sealing surface) is smaller than that of the shut-off valve, so when the valve is fully open, the flow rate is linear and the pressure of the fluid is lowered.

The disadvantage is that it takes a certain time to open and close. The flat valve plate is at right angles to the direction of fluid flow. When the ridge diameter is large, the pressure on the valve plate is also increased, which will deform the valve plate and the valve body.

Be careful when using it, it is not suitable for the half-open state from the perspective of the valve plate installation, but should be used for the fully open or fully closed state.

Shutdown valve

The shape of the shut-off valve body is "jade", so it is also called jade valve. It is structurally suitable for adjusting the flow rate and is used in most cases for the fully closed state.

Check valve

is a valve used to prevent reverse flow of fluid.

It works by backflow caused by the fluid and the back pressure acting on the valve plate, so that the check valve is automatically closed.

For this reason, when the back pressure on the valve plate is insufficient, a leak often occurs. Its shape is three types: swing type, lift type and ball type.


It consists of a plug and a valve body. It features a handle that rotates 90" and can be fully closed or fully open. 2 The flow path is a straight line and is very slippery.

It has the disadvantage that 1 because the sealing surface is large, the sealing performance is poor; 2 the handle is heavy, so in order to eliminate this disadvantage, the lubricating oil is often applied on the sealing surface and forced lubrication.

The cock is easy to operate and is used for normal temperature and atmospheric pressure pipes of water, air and gas.

Ball Valve

The spool is a sphere, so it is called a ball valve.

The general core is made of metal, but the seat is mostly non-metallic (such as Teflon). The operation is also the same as the cock, the handle can only be rotated by 90°, but compared with the cock, the sealing area of ​​the ball valve is small and the operating torque is small.

Because the spool is spherical, the fluid resistance is small, and the flow path can be changed in more than two directions due to the opening of the hole in the flow path, and is widely used in liquid discharge equipment and general chemical equipment.

The spool and bonnet are also available in all-purpose, for use in comparatively high temperatures and high pressure piping.

Butterfly valve

It consists of a valve body and a disc-shaped valve body with a stem as the shaft, and is opened and closed by the rotation of the valve body. The utility model has the advantages of simple structure, small sealing surface spacing, easy operation and good flow regulation characteristics.

In general, it is difficult to completely close the fluid when fully closed, and is usually used for large diameter, low pressure gas.

Separation valve

The diaphragm valve is composed of a valve housing and a diaphragm corresponding to the valve core. Its operating mechanism is the movement of the diaphragm. The middle of the valve housing has a sealing seat that is operated by a hand wheel to raise or lower the diaphragm to open and close the flow path.

The internal structure of the valve body is very simple. The inside of the valve body is usually lined with glass, enamel, synthetic resin, rubber, etc., and the diaphragm is made of rubber and synthetic resin. These valves are suitable for corrosive fluids because they are smooth and are often used to contain mud.

Leverage safety valve - put a weight on one end of the lever and the load on the other end.

Spring-balanced safety valve—One end of the lever balances the load on the spool with the action of a magazine.

Others—It is necessary to prevent the pressure from rising to cause an explosion, and to ensure the necessary airtightness under working conditions. In this case, a thin metal plate can be used to make an explosion-proof membrane type safety device.

Safety valves are used for steam and gas, and relief valves are used for liquids. The working mechanisms of the two are slightly different. There are many regulations for safety valves, so when selecting, the most important thing is to adapt to the relevant regulations.

The steam trap automatically removes condensate from the vapor line. There are disc type, float type, double gold type, bucket type and so on.

Other special valves include rubber, synthetic resin-lined housings, throttles for closed flow paths, and vacuum valves for vacuum systems.

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